KR102146445B1 - Luminous thin film and organic electroluminescent device - Google Patents

Abstract

An object of the present invention is to provide a luminescent thin film having high luminous efficiency and a long luminous life, and an organic electroluminescent device with improved continuous driving stability using the same. The luminescent thin film of the present invention is characterized by containing a phosphorescent metal complex and a host compound that forms an exciplex with the phosphorescent metal complex.

Description

Luminous thin film and organic electroluminescent device

The present invention relates to a light emitting thin film and an organic electroluminescent device. More specifically, it relates to a light-emitting thin film having high luminous efficiency and a long luminous life, and an organic electroluminescent device having improved continuous driving stability (half life) by using the same.

Organic electroluminescence (also referred to as ``organic EL'') is an electro-excitation light emission by recombination of electrons and holes (protons are collectively referred to as ``carrier''), so it has high luminous efficiency and eliminates all harmful substances such as mercury. Since it is not used, it has begun to be used in electronic displays, lighting, illuminations and lighting.

In addition, in an organic electroluminescent device, unlike a light emitting diode (LED), since the part responsible for light emission is generally an amorphous thin film containing an organic compound, light emission is not a point, but a maximum of about 10 square centimeters. Uniform large-area light emission is also possible, and it is also possible to make it flexible by using a flexible substrate.

In addition, in the manufacturing method, there is basically no restriction when a thin film of several tens of nanometers is formed, so coating methods such as spin coating, die coating, printing methods such as flexo printing, screen printing, etc. Furthermore, on-demand printing methods such as inkjet printing and nozzlejet printing can also be applied, and since pixels can be formed relatively easily by using a shadow mask in the heat evaporation method, it is currently used in smartphones and televisions.

Naturally, when used as an industrial product, particularly as an electronic device for private use, its power consumption becomes important. As described above, the organic EL light-emitting method generates light by recombination of electrons and holes, and therefore, compared with conventional CRT color TVs (CRDs) and incandescent bulbs, power consumption is low and environmental suitability is high. However, since modern LEDs exhibit very high luminous efficiency, it is difficult to say that an organic EL element still has a great advantage compared to a liquid crystal display or LED lighting in which it is used as a light source.

Here, two types of light emitting mechanisms in the organic EL device will be described.

When the light-emitting material present in the light-emitting layer of the organic EL element is fluorescent, the work of a light-emitting material (conventionally, because a small amount is doped and used, it is referred to as a "light-emitting dopant" or simply "dopant") by electric field excitation. It emits light by emitting fluorescence from the singlet excited state. That is, the light emitting mechanism becomes "fluorescent light emission".

On the other hand, when the light-emitting material is phosphorescent, since it emits phosphorescence and emits light from the triplet excited state of the light-emitting dopant by electric field excitation, the light-emitting mechanism becomes "phosphorescent light emission".

Usually, all organic compounds are singlet in a ground state. When it is excited by light, since it does not involve spin reversal, it must be in a singlet excited state, and if it does not emit heat when it returns to the ground state from that state, that is, if all excitons are radiation deactivated, 100% quantum It is possible to emit light with efficiency, but in the case of excitation with electricity (electric field), since the direction of electron spin is random, only 25% of the singlet excited state is generated in probability, and the remaining 75% is the triplet excited state. It becomes.

In order to change from the triplet excited state to the singlet excited state, a prohibition transition accompanied by spin inversion is required. In this case, normally, all of them are thermally deactivated (no radiation deactivated), and no light can be obtained at all. That is, although it is obvious that phosphorescence is desirable mechanically, the phosphorescence phenomenon does not occur in an organic EL device in which a conventionally generally known "classic" fluorescent material is used for the light emitting layer.

What was conceived with such a situation as a background is a phosphorescent organic EL device using a transition metal complex found by a group such as Forest of Princeton University (see, for example, Non-Patent Document 1).

In a complex of a transition metal having a large atomic weight such as platinum or iridium, the electron transition accompanying the spin reversal from the triplet to the singlet and from the singlet to the triplet as the above prohibitive transition is accelerated by the heavy atom effect, and the ligand is Depending on the selection, it has been found that there is a complex in which phosphorescent light emission with almost no radiation deactivation is obtained, thereby making it possible to realize an organic EL device with high light emission efficiency.

In fact, as of 2015, this phosphorescent light emission is applied to both smart phones and televisions, as well as red and green light emission.

However, for blue light emission, conventional fluorescent light emission is used, and an organic EL element using blue phosphorescence and a display using the same have not yet been put into practical use.

The specificity of blue phosphorescent light emission, difficulty in practical use, etc. will be described in detail later, but in general, when forming the light emitting layer of an organic EL device using a phosphorescent compound, concentration quenching or triplet-triple of the phosphorescent compound Formed by dispersing the phosphorescent compound (so-called ``dopant'') in the light-emitting layer at an appropriate concentration in a matrix containing a charge (carrier) conductive compound called a ``host compound'' in order to suppress extinction due to anti-extinguishing There are many cases.

Therefore, in such a light emitting layer, it is known that the interaction of the dopant with the host compound and the host compound has an influence as a factor that governs the efficiency and lifetime of phosphorescent light emission, and based on these findings, the improvement of light emission efficiency, etc. Research and development are progressing.

For example, a technique has been proposed to form an exciplex with two kinds of host compound molecules, a host compound functioning as an electron donor and a host compound functioning as an electron acceptor, and transfer energy to a dopant (for example, patent See document 1). In terms of reducing the probability of generating triplet excitons in a host compound with a long exciton life, which is a factor in the generation of a quencher (quenching agent), this technique can be said to be one of the means of reducing the decrease in luminous efficiency due to quenching. have.

However, in this technique, since exciplexes are formed between two molecules of the host compound, it can be easily imagined that the probability of contact between the host molecules in the vicinity of the dopant is greatly reduced. That is, the host compound in the vicinity of the dopant that most affects luminescence is considered to be in a state where the probability of becoming a triplet exciter is increased, and the effect is considered to be in a state in which the effect is not sufficiently exhibited, so there is room for further improvement such as luminous efficiency .

Japanese Patent Application Publication No. 2012-186461

M.A.Baldo et al., nature, vol. 395, pages 151 to 154 (1998)

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to provide a luminescent thin film having high luminous efficiency and a long luminous life, and an organic electroluminescent device with improved continuous driving stability (half life) using the same. Is to do.

That is, the said subject is solved by the following structure.

1. A luminescent thin film comprising a phosphorescent metal complex and a host compound that forms the phosphorescent metal complex and exciplex.

2. The luminescent thin film according to item 1, wherein the phosphorescent metal complex has a structure represented by the following general formula (1) and has a property of emitting light at room temperature.

[In the general formula (1), M represents Ir or Pt. Each of A ₁ , A ₂ , B ₁ and B ₂ represents a carbon atom or a nitrogen atom. Ring Z ₁ represents a 6-membered aromatic hydrocarbon ring formed together with A ₁ and A ₂ , or a 5-membered or 6-membered aromatic heterocycle. Ring Z ₂ represents a 5- or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ . _One of the bonds of A ₁ and M and the bond of B ₁ and M is a coordination bond and the other represents a covalent bond. Ring Z ₁ and ring Z ₂ may each independently have a substituent, but at least one of the rings has a substituent having a structure represented by the general formula (2). By bonding the substituents of the ring Z ₁ and the ring Z ₂ , a condensed ring structure may be formed, or the ligands represented by the ring Z ₁ and the ring Z ₂ may be connected to each other. L represents a monoanionic bidentate ligand coordinated with M, and may have a substituent. m represents the integer of 0-2. n represents the integer of 1 to 3. When M is Ir, m+n is 3, and when M is Pt, m+n is 2. When m or n is 2 or more, the ligand or L represented by the ring Z ₁ and the ring Z ₂ may be the same or different, respectively, and the ligand and the L represented by the ring Z ₁ and the ring Z ₂ may be connected.

In the general formula (2), * represents a linking point of the ring Z ₁ or ring Z ₂ in the general formula (1). L'represents a single bond or a linking group. Ar represents an electron acceptor substituent)

3. A property that contains at least two host compounds, and at least one of them can form an exciplex with the phosphorescent metal complex, and can form an exciplex with other host compounds. The light-emitting thin film according to claim 1 or 2, having a.

4. The luminescent thin film according to any one of items 1 to 3, wherein the phosphorescent metal complex and the host compound forming the exciplex are a compound exhibiting a thermally active delayed fluorescence.

5. The energy level of the lowest air orbit of the phosphorescent metal complex is referred to as LUMO(D),

The energy level of the highest target orbital of the host compound forming the phosphorescent metal complex and the exciplex is called HOMO (H), and

When the singlet energy of excitation of the phosphorescent metal complex and the host compound is compared, and the lower energy level of any is S ₁ (min),

The light-emitting thin film according to any one of claims 1 to 4, which satisfies the following formula (I).

Equation (I):

6. An organic electroluminescent device having at least a light-emitting layer between the anode and the cathode, wherein the light-emitting layer comprises at least the light-emitting thin film according to any one of claims 1 to 5. Nessense element.

According to the above means of the present invention, it is possible to provide a light-emitting thin film having high luminous efficiency and a long luminous life, and an organic electroluminescent device having improved continuous driving stability (half life) by using the same.

Although it is not clear about the expression mechanism or the mechanism of action of the effect of the present invention, it is speculated as follows.

When the phosphorescent metal complex (dopant) and the host compound according to the present invention are used, the phosphorescent metal complex (dopant) and the host are obtained immediately after film formation and during driving, even if an undesirable intermolecular interaction form as described below is taken. When the compound forms an exciplex, the probability that the host compound in the vicinity of the phosphorescent metal complex becomes a triplet exciter is reduced.

As a result, the generation of the phosphorescent light-emitting metal complex in the vicinity of the phosphorescent metal complex is also reduced, thereby enabling a longer life of the phosphorescent organic electroluminescent device. As a light emitting mechanism, the following two types can be considered.

That is, when the excitation energy of the exciplex is lower than the excitation energy of the phosphorescent metal complex (dopant) itself, exciplex emission is observed on the longer wavelength side than the phosphorescence emission, and the excitation energy of the exciplex is the excitation energy of the dopant and the host compound itself. In the case of equal to or higher than, the energy transfer to the phosphorescent metal complex (dopant) or the host compound competes with the light emission of the exciplex itself, and the exciplex light emission, which cannot move energy, emits light in a short wavelength region (see Fig. 8). .

Furthermore, the dispersion stability of the dopant is improved by the interaction between the molecules in the ground state of the electron acceptor of the phosphorescent metal complex (dopant) and the electron donor of the host compound, so that it is difficult to cause a decrease in luminescence due to so-called concentration quenching. I think I lose.

Further, in the studies of the present inventors so far, it has been considered that the formation of an exciplex of a phosphorescent metal complex and a host compound is unnecessary or a phenomenon to be avoided in the phosphorescent light emission process.

Because, the phenomenon of exciplex formation has an effect of increasing luminous efficiency by setting the energy levels of the excitation singlet and the excitation triplet to a level that approximates each other for a fluorescent compound that is heat deactivated from the excitation triplet state. It is generally known.

However, in the case of a phosphorescent metal complex capable of phosphorescent light emission from the excited triplet state, it has been considered as an unnecessary phenomenon. Figure 1 shows the energy level diagram of a general phosphorescent metal complex (dopant) and a host compound (hereinafter, also referred to as a host in the figure). In this way, since the HOMO of the dopant is at a higher energy level than that of the host compound, no exciplex is formed, and the dopant excitons themselves emit light. On the contrary, as shown in FIG. 2, the fact that the phosphorescent metal complex and the host compound form an exciplex is a case where the HOMO of the host compound has a higher energy level than the highest point orbit (HOMO) of the phosphorescent metal complex itself, so the emission wavelength is Since it has a longer wavelength, it has been considered a phenomenon to be avoided, particularly in a blue phosphorescent metal complex requiring short-wavelength emission.

However, as a result of intensive studies, the present inventors have found that the durability of the luminescent thin film containing the phosphorescent metal complex and the host compound that forms the exciplex is very excellent, and that the combination of the phosphorescent metal complex and the host compound must be It was found that the exciplex emission wavelength did not become longer, and thus the present invention was reached.

In addition, the means of the present invention is also effective as a green or red phosphorescent dopant, as can be seen from the speculation regarding the above mechanism, but it is more suitable to apply it to a blue phosphorescent dopant that is most susceptible to influence.

1 is an energy level diagram of a general dopant and a host compound.
2 is an energy level diagram of a dopant and a host compound according to the present invention.
3 is a conceptual diagram of a form of interaction between a dopant and a host compound.
Fig. 4 is a schematic perspective view showing an example of a display device using the organic EL element of the present invention.
Fig. 5 is a schematic perspective view showing an example of the configuration of the display portion A shown in Fig. 4;
Fig. 6 is a schematic perspective view showing an example of a lighting device using the organic EL element of the present invention.
7 is a schematic cross-sectional view showing an example of a lighting device using the organic EL element of the present invention.
8 is an example of an emission spectrum of a luminescent thin film.
9 is a conceptual diagram showing various aspects of exciplex formation.

The luminescent thin film of the present invention is characterized by containing a phosphorescent metal complex and a host compound that forms an exciplex with the phosphorescent metal complex. This feature is a technical feature common to the invention according to each claim.

As an embodiment of the present invention, it is preferable that the phosphorescent metal complex has a structure represented by the general formula (1) and emits light at room temperature from the viewpoint of the effect of the present invention.

In addition, in order to further enhance the effect of the present invention, at least two host compounds are contained, and at least one of them is capable of forming exciplex with the phosphorescent metal complex, and other types of host compounds It is desirable to have a property capable of forming an exciplex between each other.

In addition, from the same viewpoint, it is preferable that the host compound forming the phosphorescent metal complex and the exciplex is a compound exhibiting thermally active delayed fluorescence.

In an embodiment of the present invention, the energy level of the lowest pore orbit of the phosphorescent metal complex is referred to as LUMO (D), and the energy level of the highest target orbital of the host compound forming an exciplex with the phosphorescent metal complex is determined. It is referred to as HOMO (H), and when the excitation singlet energy of the phosphorescent metal complex and the host compound is compared, and the lower energy level of any is S ₁ (min), the above formula (I) is satisfied. It is desirable.

That is, when either the phosphorescent metal complex or the host compound enters an excited singlet state and satisfies the above formula (I), the other ground state than the energy of the excited singlet state [S ₁ (min)] This is because the energy of the exciplex formed by interacting with [LUMO(D)-HOMO(H)] is more stable, and thus exciplex is generated preferentially.

The light-emitting thin film of the present invention can be suitably applied to a light-emitting layer of an organic electroluminescent device.

In addition, in the present invention, in the formula (I), the energy level of the lowest orbit (LUMO), the energy level of the highest point orbit (HOMO), and the singlet energy level (S ₁ ) of each compound are: It can be obtained by the method of.

Gaussian98 (Gaussian98, Revision A. 11.4, MJFrisch, et al, Gaussian, Inc., Pittsburgh PA, 2002), a molecular orbital calculation software manufactured by Gaussian, USA, was used, and B3LYP/6-31G* was used as a keyword. It can be obtained as a calculated value (eV unit conversion value) by performing structure optimization. The reason why this calculated value is valid is because the correlation between the calculated value obtained by this method and the experimental value is high.

Hereinafter, basic matters related to the present invention will be described from the viewpoint of the principle and the mechanism before detailed description of the light-emitting thin film and its constituent elements of the present invention. In addition, in this application, "to" is used for the meaning including the numerical value described before and after that as a lower limit value and an upper limit value.

1. Specificity of blue phosphorescence

Consider the reason why blue phosphorescence emission is difficult.

First of all, the magnitude of the energy level difference between the excited state and the ground state of a molecule is one of the causes.

Almost all of carbon, nitrogen, oxygen, sulfur and other metal elements forming organic compounds form molecules by covalent bonds. These covalent bonds have an energy level required for decomposition, referred to as bond dissociation energy, but are easily decomposed by ultraviolet rays or electric fields.

However, by using a stabilization method called π conjugation, it is possible to solidify the molecule itself, and by expanding the π conjugate to form a large degenerate π conjugate, the instability peculiar to organic compounds can be significantly eliminated.

However, as the π conjugation increases, the energy level difference between the excited state and the ground state becomes narrower, and the light emission becomes longer in wavelength, that is, the red shift becomes.

Moreover, even more inconvenient is that the triplet excited state (T ₁ ) is always at a position where the energy level (level) is lower than that of the singlet excited state, so when it is fluorescent, it is green or red, which is a longer wavelength than blue in fluorescence. It becomes a mania.

For example, anthracene that emits fluorescence in a blue-violet color is phosphorescent light when it is lowered to a low temperature, but the light emission color in that case becomes red.

Therefore, in order to make a green phosphorescent substance into a red phosphorescent substance, it is accomplished by bringing the molecule (complex) in a more stabilizing direction, but in order to make it blue, it must be taken in a direction that weakens the π conjugation property. This destabilizes the molecule itself.

In addition, since the host compound, which serves to transfer energy or carriers to the luminescent dopant, decreases the luminous efficiency if the reverse energy transfer from the dopant to the host compound is not completely prevented, the energy level difference between the excited state and the ground state is reduced. It is necessary to widen it further, and this is also one of the factors that shorten the light emission life.

Next, it is the energy transfer to the quenching material (?? destination) that has a great influence. It is known that in organic EL devices, light emission is inhibited by a very small amount of water or impurities.

The reason for this is that their presence causes energy to be absorbed from the luminescent dopant in the excited state.

As described above, since the energy level of the triplet excited state of the blue phosphorescent dopant is lower than that of the green and red phosphorescence, it is easy to be affected by the energy generated in the device with time, and the reaction rate is Since it is about 100 to 10,000 times that of the green phosphorescent dopant, it can be said that it hinders the longer life of light emission.

In addition, even when compared with a blue fluorescent dopant having the same luminous color, the S ₁ energy of the blue fluorescent dopant is equal to the T ₁ energy of the blue phosphorescent dopant of the same luminescent color. The energy is lowered, and for the same reason as above, the extinction speed by the?

In addition, the phosphorescent dopant undergoing the forbidden transition has an exciton half-life (excitation lifetime) of about 100 to 1000 times as compared to the fluorescent dopant that returns to the ground state by the allowable transition, which is also a cause of increasing the extinction rate. Since, it synergistically exerts a bad influence, the light emission life of the blue phosphorescent organic EL element is short, which is the biggest factor that hinders practical use in organic EL displays.

2. The role of host compounds and dopants, and fundamental problems derived therefrom

In the light-emitting layer of an organic EL device, in principle, it is sufficient to form only a light-emitting material, in that almost all fluorescent light-emitting materials or phosphorescent light-emitting materials, when present at a high concentration, cause concentration quenching due to interactions between molecules. In addition, it is necessary to organize the environment so as not to cause multimolecular aggregation between luminescent materials by diluting with appropriate materials. Therefore, in general, a light emitting layer is formed by coexisting a material called a host compound with a light emitting dopant.

As a role of the host compound, in addition to preventing the concentration quenching, it is required to have a function of transferring electric field energy to the dopant or a function of passing carriers of either electrons or holes to the dopant.

In order for the dopant to emit light, energy may be transferred from the excitons of the host compound to emit light, or where the dopant exists as a radical anion, holes may be passed from the host compound to emit light as excitons. Conversely, of course, a mechanism for passing electrons from a host compound to a dopant that is a radical cation may be used. As a result, it is necessary to improve the luminous efficiency of the organic EL device that the dopant is efficiently excited. It doesn't matter anything.

In fact, in the case of a red phosphorescent organic EL device, it is known that both a mechanism that emits light by energy transfer from a host compound (energy transfer mechanism) and a mechanism that emits light by carrier transfer from a host compound (carrier trap mechanism) coexist. .

Even in the case of blue phosphorescence, depending on the molecular structure of the light-emitting dopant, the molecular structure of the host compound, and the layer structure of the organic EL element, both the energy transfer mechanism and the carrier trap mechanism can be used, but between the above-described excited state and the ground state. As explained in the energy level difference problem of, the host compound of a blue phosphorescent device requires an energy level difference between the excited state and the ground state, which is wider than that of the blue phosphorescent dopant, so in principle, decomposition or denaturation in the excited state is suppressed. It is difficult to do so, and as a result, it is known from the research of the present inventors that the longer the lifespan of the light-emitting element is lowered the probability of the host compound becoming excited.

On the other hand, not creating an excited state of the host compound in the light emitting layer of a blue phosphorescent device at all is basically impossible with an active action, i.e., molecular design or layer design, and an excited state of the host compound will necessarily occur to some extent. .

Particularly, it is fatal as a light emission lifetime for the host compound to become a triplet excited state with a long exciton existence time, but as described above, 75% of the electric field excitation becomes triplet excitons, and furthermore, it does not have a heavy atom in the molecule. In the case of the host compound, the existence time of the triplet excitons becomes several orders of magnitude longer than that of the dopant, which becomes a big problem.

3. How to extend the light emission life of blue phosphorescence

3.1 Fastening of the luminescent material (dopant) itself

The first step in prolonging the light-emitting lifetime of a blue phosphorescent device is to stabilize the light-emitting material, the dopant itself.

In general, the phosphorescent dopant is derived from the fact that orthometalized complexes of platinum or iridium are used, and these complexes are very stable thermally and electrochemically. However, the lifespan is still too short for application to electronic displays.

3.2 Suppression of heat generation by improving luminous efficiency

In addition to these fundamental improvements, improvement techniques peculiar to organic EL devices are also being developed.

When an organic EL element is expressed as an electric equivalent circuit, it is expressed as a resistor and a diode. That is, Joule heat is generated inside the device by always passing current.

Organic EL devices are characterized by being a stack of amorphous films formed of organic compounds, whereas, on the other hand, a luminescent thin film formed of organic compounds has a glass transition temperature (Tg), and if the temperature exceeds that temperature even locally, molecules will move. It starts to perform, crystallization, or phase-to-phase shift, resulting in an undesirable phenomenon in the light emission lifetime of the organic EL element.

The source of this Joule heat, in extreme terms, is due to the non-radiation deactivation of molecules, and the higher the luminous efficiency, the less heat generated, but the luminous efficiency and the luminous lifetime are also dependent on the type of material used, the thickness of the layer, and the layer composition. Because it changes dramatically, there are few reports of quantitative research examples.

Objectivity is lacking, but in a blue phosphorescent device whose luminous efficiency of the organic EL device has been raised to close to the theoretical limit, as a result of the inventors' long-standing research on blue phosphorescent organic EL, the higher the luminous efficiency, the longer the luminous life. Loss has also been demonstrated, and this is an important factor as a viewpoint toward longer life in that it suggests that the two performances of the organic EL device are not traded off.

3.3 What is the fundamental problem of short life of blue phosphorescent device?

Here, let's take a look at the fundamental causes in the light emission lifetime of the blue phosphorescent device.

(1) Widening the energy level difference between the excited state and the ground state of the luminescent dopant and the host compound directly leads to the fragility of the molecule.

(2) Due to the two synergistic effects of the light-emitting dopant having a low triplet excited state energy level and a long triplet photoexcitation life, the extinction speed by the luminescent dopant becomes very fast.

(3) A host compound having a wider difference in energy level between the excited state and the ground state than the luminescent dopant becomes an exciter, especially when it becomes a triplet exciter, which triggers the decomposition product, reaction product, aggregate, etc.? The wife is created.

In other words, how to solve these problems is indispensable in order to put the blue phosphorescent organic electroluminescence device into practical use, and the inventors of the present invention have repeatedly studied intensively over the years to solve the problem, as a result of the molecular interaction between the phosphorescent dopant and the host compound. I came to the conclusion that it was important. The present invention is a completely new technology concept that solves the fundamental problem and cannot be found otherwise, and also provides a practical technical means.

4. Molecular interaction between phosphorescent dopant and host compound

4.1 Intermolecular interaction states of dopant and host compound

In order to improve the luminous efficiency, as described in Item 2 above, since the phosphorescent dopant enters the excited state, it can be said that it is a necessary condition to transfer electrons from the radical anionic host compound to the radical cationic dopant.

In addition, as described in Section 3.3 above, it is necessary to suppress the formation of triplet excitons in the host compound so as not to generate a spot. In other words, it can be said that in order to extend the life of the phosphorescent element, the two necessary conditions must be maintained immediately after film formation and with the elapse of device driving.

Consider this requirement at the molecular level.

There are two types of interaction states of the host compound close to the LUMO orbital, which is the electron-receiving site of the phosphorescent dopant (see Fig. 3).

1) The LUMO orbital of the host compound exists near the LUMO orbital of the dopant.

2) In the vicinity of the LUMO orbital of the dopant, the HOMO orbital of the host compound exists.

In the case of 1), electrons are rapidly transferred from the radically anionic host compound to the dopant, so that the dopant excitons are easily formed, and the triplet excitons of the host compound are difficult to form.

On the other hand, in the case of 2), electron transfer from the host compound in a radical anion state to the dopant is difficult to occur, during which holes are trapped on the host compound and carrier recombination occurs, thereby forming excitons of the host compound. In this case, the singlet excitons (25%) of the host compound are rapidly energy transferred to the adjacent dopant and there is no loss, but the triplet excitons (75%) are dexter energy transfer to the dopant and non-radiation deactivation due to the length of the exciton lifetime. It becomes a competitive process of energy loss, or the formation of decomposition products, reaction products, aggregates, etc. by thermal host molecule motion, which is accompanied by undesirable state changes.

4.2 Changes in Molecular Interactions in Phosphorescent Device Electric Field Driving

Next, this molecular state is further considered from the viewpoint of fluctuations before and after driving the device.

Immediately after film formation, the dopant and the host compound are in an amorphous state (random orientation), and the above 1) and 2) are likely to occur at approximately equal frequencies.

However, by driving the device, molecules repeat molecular motions such as a radical state or an excited state hundreds of millions of times from the ground state, and in the process, the molecules in the organic layer change to a more thermally and electrically stable state. The electrically stable state means that the state changes from 1) in the electrical repulsion state to 2) in the electrical stable state, similar to the behavior of the magnet. That is, during driving, it can be imagined that the light-emitting characteristics are deteriorated to 2) in the form of an interaction between molecules of the dopant and the host compound, which is not desirable (see Fig. 3).

In this way, when the dopant and the host compound are in an electrically stable state, the probability that the host compound becomes a triplet exciter increases, and as a result, it is easy to cause alteration such as aggregation or decomposition. The deterioration of this host compound becomes a place where the luminous energy of the dopant is deprived, accompanied by a decrease in luminescence properties. Naturally, the closer the distance between the dopant and the destination is, the easier it is for the excitation energy of the dopant to be taken away, and the luminescence property decreases. That is, it can be said that suppressing the deterioration of the host compound in the vicinity of the dopant is very important for maintaining the luminescence property, that is, increasing the life of the device.

Hereinafter, the light-emitting thin film of the present invention and its constituent elements will be described in detail.

≪Light-emitting thin film≫

The luminescent thin film of the present invention is characterized by containing a phosphorescent metal complex and a host compound that forms an exciplex with the phosphorescent metal complex.

The formation of exciplex can be seen by comparing the emission spectra of the phosphorescent starting metal complex and the host compound. When the exciplex is formed, the emission spectra of each single element of the phosphorescent starting metal complex and the host compound have peaks in different regions.

As an embodiment of the present invention, it is preferable that the phosphorescent metal complex has a structure represented by the following general formula (1) and emits light at room temperature from the viewpoint of the effect of the present invention.

The content of the phosphorescent metal complex or host compound in the light-emitting thin film of the present invention can be arbitrarily determined based on the conditions required for the product to be applied, and is contained in a uniform concentration with respect to the layer thickness direction of the light-emitting layer. It may be present or may have an arbitrary concentration distribution.

However, the content of the phosphorescent metal complex according to the present invention is preferably 1 to 50% by mass, and 1 to 30% by mass when the mass of the luminescent thin film is 100% by mass in order to appropriately express the luminescence phenomenon. More preferable. In addition, the content of the host compound according to the present invention is preferably 50 to 99% by mass, and more preferably 70 to 99% by mass, when the mass of the luminescent thin film is 100% by mass.

Next, the "phosphorescent metal complex" and the "host compound" contained in the luminescent thin film according to the present invention will be described in detail.

≪Phosphorescent metal complex≫

In the present invention, a preferred phosphorescent metal complex is a metal complex having a structure represented by the following general formula (1).

[In the general formula (1), M represents Ir or Pt. Each of A ₁ , A ₂ , B ₁ and B ₂ represents a carbon atom or a nitrogen atom. Ring Z ₁ represents a 6-membered aromatic hydrocarbon ring formed together with A ₁ and A ₂ , or a 5-membered or 6-membered aromatic heterocycle. Ring Z ₂ represents a 5- or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ . _One of the bonds of A ₁ and M and the bond of B ₁ and M is a coordination bond and the other represents a covalent bond. Ring Z ₁ and ring Z ₂ may each independently have a substituent, but at least one of the rings has a substituent having a structure represented by the general formula (2). By bonding the substituents of the ring Z ₁ and the ring Z ₂ , a condensed ring structure may be formed, or the ligands represented by the ring Z ₁ and the ring Z ₂ may be connected to each other. L represents a monoanionic bidentate ligand coordinated with M, and may have a substituent. m represents the integer of 0-2. n represents the integer of 1 to 3. When M is Ir, m+n is 3, and when M is Pt, m+n is 2. When m or n is 2 or more, the ligand or L represented by ring Z ₁ and ring Z ₂ may be the same or different, respectively, and the ligand and L represented by ring Z ₁ and ring Z ₂ may be connected.

In the general formula (2), * represents a linking point of the ring Z ₁ or ring Z ₂ in the general formula (1). L'represents a single bond or a linking group. Ar represents an electron acceptor substituent)

When ring Z ₁ represents a 6-membered aromatic hydrocarbon ring, as the 6-membered aromatic hydrocarbon ring, a benzene ring, as an example in which an aromatic hydrocarbon ring is condensed with the 6-membered aromatic hydrocarbon ring, further includes a naphthalene ring, an anthracene ring, etc. Can be lifted.

When ring Z ₁ represents a 5-membered or 6-membered aromatic heterocycle, examples of the 5-membered aromatic heterocycle include a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, a tetrazole ring, an oxazole ring, and isoxa A sol ring, a thiazole ring, an isothiazole ring, an oxadiazole ring, a thiadiazole ring, etc. are mentioned.

Among these, a pyrazole ring and an imidazole ring are preferable, and an imidazole ring is more preferable. These rings may be further substituted with a substituent selected from the following substituent groups. Preferred as the substituent are an alkyl group and an aryl group, and more preferably a substituted alkyl group and an unsubstituted aryl group.

Moreover, as a 6-membered aromatic heterocycle, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, etc. are mentioned.

Ring Z ₂ is preferably a 5-membered aromatic heterocycle, and examples of the 5-membered aromatic heterocycle include a 5-membered aromatic heterocycle represented by ring Z ₁ . In particular, it is preferable that at least one of B ₁ and B ₂ is a nitrogen atom.

As the substituent in the general formula (1) (other than the substituent represented by the general formula (2)), for example, an alkyl group (e.g., methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group , Hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group , Allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (aromatic hydrocarbon ring group, aromatic carbocyclic group, aryl group, etc.), for example, phenyl group, p-chlorophenyl group, Mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group ( For example, pyridyl group, pyrazyl group, pyrimidinyl group, triazyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzooxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group , Furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, azacarbazolyl group (of the carbazolyl group Indicates that any one or more of the carbon atoms constituting the carbazole ring is substituted with a nitrogen atom), quinoxalinyl group, pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (e.g. For example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (e.g., methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group) , Dodecyloxy group, etc.), cycloalkoxy group (e.g., cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (e.g., phenoxy group, naphthyloxy group, etc.), alkylthio group (e.g. For example, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (e.g., cyclopentylthio group Group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, Dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (e.g., phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (e.g., aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylamino Sulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (e.g. For example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (e.g. For example, an acetyloxy group, an ethylcarbonyloxy group, a butylcarbonyloxy group, an octylcarbonyloxy group, a dodecylcarbonyloxy group, a phenylcarbonyloxy group, etc.), an amide group (e.g., methylcarbonyl Amino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonyl Amino group, naphthylcarbonylamino group, etc.), carbamoyl group (e.g., aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexyl group, etc.) Aminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (e.g., methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, Octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (e.g., methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulphi) Neil, 2-E Tylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (e.g., methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexyl) Sulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (e.g., phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group ( For example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (e.g. For example, a fluorine atom, a chlorine atom, a bromine atom, etc.), a fluorinated hydrocarbon group (e.g., a fluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group, a pentafluorophenyl group, etc.), a cyano group, a nitro group, a hydroxy group, Mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), a phosphono group, etc. are mentioned.

These substituents may be further substituted by the above-described substituents, and a plurality of these substituents may be bonded to each other to form a ring structure.

Examples of the linking group of L'in the general formula (2) include a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms, and 5 to 30 ring atoms. And a divalent linking group including a heteroarylene group of or a combination thereof.

And the C1-C12 alkylene group may be linear or may have a branched structure, and may have a cyclic structure like a cycloalkylene group. Further, the arylene group having 6 to 30 ring carbon atoms may be non-condensed or a condensed ring may be used.

As the arylene group having 6 to 30 ring carbon atoms, for example, o-phenylene group, m-phenylene group, p-phenylene group, naphthalenediyl group, phenanthrenediyl group, biphenylene group, terphenylene group, quarterphenylene group, tri A phenylenediyl group, a fluorendiyl group, etc. are mentioned.

As a heteroarylene group having 5 to 30 ring atoms, for example, a pyridine ring, a pyrazine ring, a pyrimidine ring, a piperidine ring, a triazine ring, a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, an indole ring, iso Indole ring, benzimidazole ring, furan ring, benzofuran ring, isobenzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, silol ring, benzosilol ring, dibenzosilol ring, quinoline ring, iso Quinoline ring, quinoxaline ring, phenanthridine ring, phenanthroline ring, acridine ring, phenazine ring, phenoxazine ring, phenothiazine ring, phenoxatiine ring, pyridazin ring, acridine ring, oxazole ring, oxadiazole ring, Benzooxazole ring, thiazole ring, thiadiazole ring, benzothiazole ring, benzodifuran ring, thienothiophene ring, dibenzothiophene ring, benzodithiophene ring, cyclidine ring, quindrine ring, tefenidine ring, quinidine ring Ring, tripenodithiazine ring, tripenodioxazine ring, phenanthrazine ring, anthazine ring, perimidine ring, naphthofuran ring, naphthothiophene ring, benzodithiophene ring, naphtodifuran ring, naphtodithiophene ring , Anthrafuran ring, anthradifuran ring, anthrathiophene ring, anthradithiophene ring, thianthrene ring, phenoxatiine ring, naphthothiophene ring, carbazole ring, carboline ring, diazacarbazole ring (carba It indicates that any two or more of the carbon atoms constituting the sol ring are substituted with nitrogen atoms), azadibenzofuran ring (represents that any one or more of the carbon atoms constituting the dibenzofuran ring is substituted with a nitrogen atom), Derived by excluding two hydrogen atoms from the azadibenzothiophene ring (representing that at least one of the carbon atoms constituting the dibenzothiophene ring is substituted with a nitrogen atom), indolocarbazole ring, indenoindole ring, etc. The divalent flag to be used is mentioned.

As a more preferable heteroarylene group, from a pyridine ring, a pyrazine ring, a pyrimidine ring, a piperidine ring, a triazine ring, a dibenzofuran ring, a dibenzothiophene ring, a carbazole ring, a carboline ring, a diazacarbazole ring, etc. Divalent groups derived by excluding two hydrogen atoms are mentioned.

These linking groups may be substituted by the above-described substituents.

Examples of the substituent Ar having electron acceptor properties of the general formula (2) include aromatic heterocyclic groups (e.g., pyridyl group, pyrazyl group, pyrimidinyl group, triazyl group, furyl group, pyrrolyl group, imidazolyl group, benzo Imidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (eg, 1,2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxa Zolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group , Indolyl group, carbazolyl group, azacarbazolyl group (represents that at least one of the carbon atoms constituting the carbazole ring of the carbazolyl group is substituted with a nitrogen atom), quinoxalinyl group, pyridazinyl Group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), fluorohydrocarbon group (e.g., fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro Group, tosil group, acyl group, and the like.

These substituents may be further substituted by the above-described substituents or other substituents, and a plurality of these substituents may be bonded to each other to form a ring structure.

Hereinafter, a specific example of the luminescent metal complex according to the present invention is shown, but it is not limited thereto as long as the host compound and the exciplex to be combined are formed.

≪Host compound≫

The host compound according to the present invention is capable of forming a phosphorescent metal complex and an exciplex. Hereinafter, in addition to the host compound according to the first embodiment capable of forming the phosphorescent metal complex and the exciplex, at least two host compounds are contained, and at least one of them is the phosphorescent metal complex. The host compound according to the second embodiment, which can form exciplex and exciplex, and has the property of forming exciplex with other types of host compounds, further exhibits thermally activated delayed fluorescence (TADF). The host compound according to the third embodiment will be described.

<Host compound according to the first embodiment>

In order to form the LUMO orbital and the exciplex of the phosphorescent metal complex, the host compound according to the first embodiment preferably has an electron donor property in a partial structure constituting the HOMO orbital. For example, partial structures, such as carbazole, allylamine, carboline, indolocarbazole, and indoloindole, are mentioned.

Hereinafter, specific examples of the host compound according to the first embodiment of the present invention will be shown, but the present invention is not limited thereto.

<Host compound according to the second embodiment>

The host compound according to the second embodiment is composed of two types of host compounds, one host compound forms a phosphorescent metal complex and an exciplex, and also two types of host compounds can form an exciplex. Combinations that are present are preferred.

In addition, in the exciplex formed by the host compound according to the second embodiment, the interval between the level of the lowest triplet excited state and the level of the lowest singlet excited state is small, and a phenomenon of inverse crossover between both states is expressed.

Although it does not specifically limit as a combination of the host compound which forms exciplex, For example, Adv. Mater. Combination of compounds described in 2014, 26, 4730-4734, Adv. Mater. Combinations of the compounds described in 2015, 27, 2378-2383, etc. are mentioned.

Hereinafter, specific examples of the host compound according to the second embodiment of the present invention will be shown, but the present invention is not limited thereto.

<Host compound according to the third embodiment>

The host compound according to the third embodiment is a compound exhibiting thermally activated delayed fluorescence (TADF).

In addition, since the host compound according to the second embodiment exhibits thermally active delayed fluorescence, the interval between the level of the lowest triplet excited state and the level of the lowest singlet excited state is small. Manifest phenomena.

The thermally active delayed fluorescence is explained on pages 261 to 268 of "Device Properties of Organic Semiconductors" (Chihaya Adachi, published by Kodansha). In the literature, if the energy difference ΔE between the excited singlet state and the excited triplet state of a fluorescent light emitting material can be made small, the reverse energy transfer from the excited triplet state with a low transition probability to the excited singlet state is highly efficient. As a result, it has been described that thermally activated delayed fluorescence (TADF) is expressed. Further, in Fig. 10.38 in this document, the mechanism of generating delayed fluorescence is described. The host compound according to the third embodiment is a compound exhibiting thermally activated delayed fluorescence generated by such a mechanism. The delayed fluorescence emission can be confirmed by transient PL measurement.

The transient PL is a method of irradiating a sample with a pulsed laser to excite it, and measuring the attenuation behavior (transient characteristic) of PL emission after the irradiation is stopped. The PL light emission in the TADF material is classified into a light emission component from a singlet excitons generated by the first PL excitation and a light emission component from a singlet excitons generated via a triplet exciton. The lifetime of singlet excitons generated by the first PL excitation is on the order of nanoseconds, and is very short. Therefore, light emission from the singlet excitons is rapidly attenuated after irradiation with a pulsed laser.

On the other hand, delayed fluorescence is gently attenuated due to light emission from singlet excitons generated via triplet excitons having a long lifetime. In this way, there is a large difference in time between light emission from singlet excitons generated by the first PL excitation and light emission from singlet excitons generated via triplet excitons. The host compound according to the third embodiment is a compound having such a luminescent component derived from delayed fluorescence.

Although it does not specifically limit as a compound which shows a thermally active type delay, For example, Adv. Mater. 2014, DOI:10.1002/adma. The compounds described in 201402532, etc. can be mentioned.

Hereinafter, specific examples of the host compound according to the third embodiment of the present invention will be shown, but the present invention is not limited thereto.

As described above, the "luminescent metal complex" and the "host compound" contained in the luminescent thin film according to the present invention have been described by dividing into a plurality of embodiments, but any combination of the "luminescent metal complex" and the "host compound" may be used. Further, while the "luminescent metal complex" of the plurality of embodiments described above may be used in combination, the "host compound" of the plurality of embodiments described above may be used in combination.

In addition, the light-emitting thin film of the present invention can be applied to various products, for example, an organic electroluminescent device, an organic thin film solar cell, and the like to be described later. In addition, the luminescent thin film of the present invention may further contain known substances commonly used when applied to each product in addition to the above-described "luminescent metal complex" and "host compound".

≪Constituent layers of organic electroluminescent devices≫

Typical device configurations in the organic EL device of the present invention include the following configurations, but are not limited thereto.

(1) anode/light emitting layer/cathode

(2) anode/light emitting layer/electron transport layer/cathode

(3) anode/hole transport layer/light-emitting layer/cathode

(4) anode/hole transport layer/light-emitting layer/electron transport layer/cathode

(5) anode/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode

(6) anode/hole injection layer/hole transport layer/light-emitting layer/electron transport layer/cathode

(7) Anode/hole injection layer/hole transport layer/(electron blocking layer/) light-emitting layer/(hole blocking layer/)electron transport layer/electron injection layer/cathode

Among the above, the configuration (7) is preferably used, but is not limited thereto.

The light-emitting layer according to the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light-emitting layers, a non-luminescent intermediate layer may be formed between the light-emitting layers.

If necessary, a hole blocking layer (also referred to as a hole barrier layer) or an electron injection layer (also referred to as a negative buffer layer) may be formed between the light emitting layer and the cathode, and an electron blocking layer (also referred to as an electron barrier layer) between the light emitting layer and the anode. ) Or a hole injection layer (also referred to as an anode buffer layer).

The electron transport layer according to the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Moreover, it may be comprised with multiple layers.

The hole transport layer according to the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, it may be comprised with multiple layers.

In the above-described typical device configuration, the layer excluding the anode and the cathode is also referred to as an "organic layer".

(Tandem structure)

Further, the organic EL element according to the present invention may be an element having a so-called tandem structure in which a plurality of light-emitting units including at least one light-emitting layer are stacked.

As a typical element configuration of a tandem structure, the following configurations are mentioned, for example.

Anode/first light emitting unit/second light emitting unit/third light emitting unit/cathode

Anode/first light emitting unit/intermediate layer/second light emitting unit/intermediate layer/third light emitting unit/cathode

Here, the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit may all be the same or different. Further, the two light emitting units may be the same, and the remaining one may be different.

Further, the third light-emitting unit may not be present, and a light-emitting unit or an intermediate layer may be further formed between the third light-emitting unit and the electrode.

A plurality of light emitting units may be directly stacked or stacked through an intermediate layer, and the intermediate layer is generally referred to as an intermediate electrode, an intermediate conductive layer, a charge generating layer, an electron extracting layer, a connection layer, and an intermediate insulating layer. A known material configuration can be used as long as it has a function of supplying electrons to the adjacent layer of and holes to the adjacent layer on the cathode side.

Examples of the material used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , a conductive inorganic compound layer such as Al, a two-layer film such as Au/Bi ₂ O ₃ , SnO ₂ /Ag/SnO ₂ , ZnO/Ag/ZnO, Bi ₂ O ₃ Multilayer films such as /Au/Bi ₂ O ₃ , TiO ₂ /TiN/TiO ₂ , TiO ₂ /ZrN/TiO ₂ , fullerenes such as C ₆₀ , conductive organic layers such as oligothiophene, metal phthalocyanines, metal-free Conductive organic compound layers, such as phthalocyanines, metal porphyrins, metal-free porphyrins, etc. are mentioned, but this invention is not limited to these.

As a preferable configuration in the light emitting unit, for example, from the configurations (1) to (7) exemplified in the above-described typical device configuration, excluding the anode and the cathode, etc. can be mentioned, but the present invention is not limited thereto. .

As a specific example of the tandem type organic EL device, for example, US Patent No. 63,374,92, US Patent No. 7420203, US Patent No. 74433923, US Patent No. 6872472, US Patent No. 61,07734, US Patent No. 6337492 Specification, International Publication No. 2005/009087, Japanese Patent Application Publication No. 2006-228712, Japanese Patent Application Publication No. 2006-24791, Japanese Patent Application Publication No. 2006-49393, Japanese Patent Application Publication No. 2006-49394 Gazette, Japanese Patent Application Publication No. 2006-49396, Japanese Patent Application Publication No. 2011-96679, Japanese Patent Application Publication No. 2005-340187, Japanese Patent No. 4711424, Japanese Patent No. 3496681, Japanese Patent No. 3884564, Japanese Patent Publication No. 4213169, Japanese Patent Publication No. 2010-192719, Japanese Patent Publication No. 2009-076929, Japanese Patent Publication No. 2008-078414, Japanese Patent Publication No. 2007-059848, Japanese Patent Publication No. Although the element structure and constituent materials described in 2003-272860 A, Japanese Patent Laid-Open No. 2003-045676, International Publication No. 2005/094130, and the like can be mentioned, the present invention is not limited thereto.

Hereinafter, each layer constituting the organic EL device of the present invention will be described.

≪Light emitting layer≫

The light-emitting layer used in the present invention is a layer that provides a place where electrons and holes injected from an electrode or an adjacent layer recombine and emit light via excitons, and the light emitting part is a layer adjacent to the light-emitting layer, even if it is in the layer of the light-emitting layer. It may be an interface of. In addition, the light-emitting layer according to the present invention is composed of the above-described "luminescent thin film".

In addition, the light emitting layer used in the present invention is not particularly limited in its configuration as long as it satisfies the requirements for the light emitting thin film specified in the present invention.

The total thickness of the layer (film) of the light emitting layer is not particularly limited, but from the viewpoint of uniformity of the film to be formed, application of unnecessary high voltage during light emission, and improvement of the stability of the light emission color against the driving current, from 2 nm to It is preferably adjusted in the range of 5 µm, more preferably in the range of 2 nm to 500 nm, and still more preferably in the range of 5 nm to 200 nm.

In addition, in the present invention, the layer thickness of each light emitting layer is preferably adjusted to a range of 2 nm to 1 µm, more preferably adjusted to a range of 2 to 200 nm, and still more preferably 3 to 150 nm. Is adjusted to the range of.

The light-emitting layer according to the present invention is constituted by containing the aforementioned "luminescent metal complex" and "host compound".

However, in the light-emitting layer according to the present invention, within a range that does not interfere with the effects of the present invention, separately shown below "(1) luminescent dopant: (1.1) phosphorescent dopant, (1.2) fluorescent luminescent dopant" or "( 2) Host compound" may be contained.

(1) luminescent dopant

The light-emitting dopant used in the present invention will be described.

As the luminescent dopant, a phosphorescent dopant (also referred to as a phosphorescent dopant or a phosphorescent compound) or a fluorescent dopant (also referred to as a fluorescent dopant or a fluorescent compound) may be used.

Further, the light-emitting dopant used in the present invention may be used in combination of a plurality of types, a combination of dopants having different structures, or a combination of a fluorescent dopant and a phosphorescent dopant may be used. As a result, an arbitrary color of luminescence can be obtained.

The emission color of the organic EL device of the present invention and the luminescent thin film of the present invention is a spectral emission luminance meter CS in Fig. 4.16 on page 108 of the 「New Color Science Handbook」 (Japanese Color Society Edition, Tokyo University Press, 1985). It is determined as the color when the result of measurement with -1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.

In the present invention, it is also preferable that one or more light emitting layers contain a plurality of light emitting dopants having different light emission colors and exhibit white light emission.

The combination of the white light-emitting dopant is not particularly limited, but examples thereof include blue and orange, and a combination of blue and green and red.

The white color in the organic EL device of the present invention is not particularly limited, and may be white close to orange or white close to blue, but CIE1931 at 1000 cd/m2 when the front luminance at a 2 degree viewing angle was measured by the method described above. It is preferable that the chromaticity in the colorimetric system is within a region of x=0.39±0.09 and y=0.38±0.08.

(1.1) phosphorescent dopant

The phosphorescent dopant (hereinafter also referred to as "phosphorescent dopant") used in the present invention will be described.

The phosphorescent dopant used in the present invention is a compound in which light emission from triplet excitation is observed, specifically, it is a compound that emits phosphorescence at room temperature (25°C), and is a compound having a phosphorescence quantum yield of 0.01 or more at 25°C. Although defined, the preferred phosphorescence quantum yield is at least 0.1.

The phosphorescence quantum yield in the present invention can be measured by the method described on page 398 (Maruzen, 1992 edition) of Spectroscopy II of the fourth edition experimental chemistry lecture 7. The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant according to the present invention may achieve the phosphorescence quantum yield (0.01 or more) in any of the solvents.

There are two types of light emission from the phosphorescent dopant. First, recombination of the carriers occurs on the host compound to which the carrier is transported to create an excited state of the host compound, and this energy is transferred to the phosphorescent dopant, thereby emitting light from the phosphorescent dopant. It is an energy transfer type to get. Another is a carrier trap type in which a phosphorescent dopant serves as a carrier trap, and carrier recombination occurs on the phosphorescent dopant to obtain light emission from the phosphorescent dopant. Also in all cases, it is a condition that the excited state energy of the phosphorescent dopant is lower than that of the host compound.

As the phosphorescent dopant that can be used in the present invention, it can be appropriately selected and used from known ones used for the light emitting layer of an organic EL device.

Specific examples of the known phosphorescent dopant that can be used in the present invention include compounds described in the following documents.

Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622(2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Publication No. 2006/835469, US Patent Publication No. 2006/0202194 , US Patent Publication No. 2007/0087321, US Patent Publication No. 2005/0244673, Inorg.Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003(2004), Angew. Chem.lnt.Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906(2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Publication No. 2002/0034656, US Patent No. 73332232, US Patent Publication No. 2009/0108737 Specification, US Patent Publication No. 2009/0039776, US Patent No. 6921915 Specification, US Patent No. 6687266 Specification, US Patent Publication No. 2007/0190359 Specification, US Patent Publication No. 2006/0008670 Specification , U.S. Patent Publication No. 2009/0165846, U.S. Patent Publication No. 2008/0015355, U.S. Patent No. 7250226, U.S. Patent No.7396598, U.S. Patent Publication No. 2006/0263635, U.S. Patent Publication 2003 /0138657 specification, US patent publication 2003/0152802 specification, US patent 700928 specification, Angew.Chem.lnt.Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, US Patent Publication No. 2006/0251923, US Patent Publication No. 2005/0260441, US Patent No. 7333599, US Patent 7534505 Specification, US Patent No. 7443855 Specification, US Patent Publication No. 2007/0190359 Specification, US Patent Publication No. 2008/0297033 Specification, US Patent No.7338722 Specification, US Patent Publication No. 2002/0134984 Specification, US Patent No.7279704 Specification, US Patent Publication No. 2006/098120, US Patent Publication No. 2006/103874, International Publication No. 2005/076380, International Publication No. 2010/032663, International Publication No. 2008/140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. 2009/113646, International Publication No. 2012/020327, International Publication 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, U.S. Patent Publication No. 2012/228583, U.S. Patent Publication No. 2012/212126, Japanese Patent Publication No. 2012-069737 Gazette, Japanese Patent Application Publication No. 2012-195554, Japanese Patent Application Publication No. 2009-114086, Japanese Patent Application Publication No. 2003-81988, Japanese Patent Application Publication No. 2002-302671, Japanese Patent Application Publication No. 2002-363552 It is a public notice.

Among them, as a preferable phosphorescent dopant, an organometallic complex having Ir in the center metal is exemplified. More preferably, a complex comprising at least one coordination mode of metal-carbon bonds, metal-nitrogen bonds, metal-oxygen bonds, and metal-sulfur bonds is preferred.

(1.2) Fluorescent dopant

The fluorescent dopant used in the present invention (hereinafter, also referred to as "fluorescent dopant") will be described.

The fluorescent dopant used in the present invention is a compound capable of emitting light from singlet excitation, and is not particularly limited as long as light emission from singlet excitation is observed.

As the fluorescent dopant used in the present invention, for example, anthracene derivative, pyrene derivative, chrysene derivative, fluoranthene derivative, perylene derivative, fluorene derivative, arylacetylene derivative, styrylarylene derivative, styrylamine derivative, Arylamine derivatives, boron complexes, coumarin derivatives, pyran derivatives, cyanine derivatives, croconium derivatives, squarylium derivatives, oxobenzanthracene derivatives, fluorescein derivatives, rhodamine derivatives, pyryllium derivatives, perylene derivatives, polythiophene Derivatives or rare earth complex compounds.

Further, in recent years, light-emitting dopants using delayed fluorescence have also been developed, and these may be used.

Specific examples of the light-emitting dopant using delayed fluorescence include, for example, the compounds described in International Publication No. 2011/156793, Japanese Patent Application No. 2011-213643, Japanese Patent Application No. 2010-93181, and the like. Is not limited to these.

(2) host compound

The host compound used in the present invention is a compound mainly responsible for injecting and transporting electric charges in the light emitting layer, and in the organic EL device, light emission of itself is not substantially observed.

Preferably, the phosphorescence quantum yield of phosphorescence at room temperature (25°C) is less than 0.1, and more preferably, the phosphorescence quantum yield is less than 0.01.

In addition, the excited state energy of the host compound is preferably higher than the excited state energy of the light emitting dopant contained in the same layer.

The host compound may be used alone or in combination of multiple types. By using a plurality of host compounds, it is possible to control the transfer of electric charges, and the organic EL device can be highly efficient.

The host compound that can be used in the present invention is not particularly limited, and a compound conventionally used in an organic EL device can be used. It may be a low molecular weight compound or a high molecular compound having a repeating unit, and may be a compound having a reactive group such as a vinyl group or an epoxy group.

As a known host compound, it has a hole-transporting ability or an electron-transporting ability, and also prevents a long wavelength of light emission, and is highly advantageous from the viewpoint of stably operating the organic EL element against heat generation during high temperature drive or element drive. It is preferred to have a transition temperature (Tg). Preferably, Tg is 90°C or higher, and more preferably 120°C or higher.

Here, the glass transition point (Tg) is a value obtained by a method conforming to JIS-K-7121 using DSC (Differential Scanning Colorimetry).

Specific examples of known host compounds used in the organic EL device of the present invention include compounds described in the following documents, but are not limited thereto.

Japanese Patent Application Laid-Open No. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860 Publications, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579 , 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002 2002-302516, 2002-305083, 2002-305084, 2002-308837, US Patent Publication No. 2003/0175553, US Patent Publication No. 2006/0280965, US Patent Publication 2005/0112407 Specification, US Patent Publication No. 2009/0017330 Specification, US Patent Publication No. 2009/0030202 Specification, US Patent Publication No. 2005/0238919 Specification, International Publication No. 2001/039234, International Publication No. 2009/ 021126, International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/063796, International Publication No. 2007/063754, International Publication No. 2004/107822 , International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898 No. 2012/023947, Japanese Patent Publication No. 2008-074939, Japanese Patent Publication No. 2007-254297, European Patent No. 2034538, and the like.

≪Electron transport layer≫

In the present invention, the electron transport layer includes a material having a function of transporting electrons, and should have a function of transferring electrons injected from the cathode to the light emitting layer.

There is no particular limitation on the total layer thickness of the electron transport layer used in the present invention, but it is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, and still more preferably 5 to 200 nm.

In addition, in the organic EL device, when light generated in the light-emitting layer is extracted from the electrode, the light directly extracted from the light-emitting layer and the light reflected by the electrode for extracting light and the electrode positioned on the opposite electrode and then extracted from the electrode cause interference. It is known. When light is reflected from the cathode, it is possible to efficiently utilize this interference effect by appropriately adjusting the total layer thickness of the electron transport layer to between 5 nm and 1 µm.

On the other hand, since the voltage tends to increase when the layer thickness of the electron transport layer is increased, the electron mobility of the electron transport layer is preferably 10 ^-5 cm 2 /Vs or more, particularly in the case of a thick layer.

As the material used for the electron transport layer (hereinafter, referred to as an electron transport material), it is sufficient to have any of electron injection or transport properties, and hole barrier properties, and any one of conventionally known compounds can be selected and used.

For example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more of the carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, and pyri Chopped derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, azatriphenylene derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, benzimidazole Derivatives, benzoxazole derivatives, benzthiazole derivatives, etc.), dibenzofuran derivatives, dibenzothiophene derivatives, silol derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene, etc.), and the like.

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton in a ligand, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) Aluminum, tris(5,7-dibromo-8-quinolinol) aluminum, tris(2-methyl-8-quinolinol) aluminum, tris(5-methyl-8-quinolinol) aluminum, bis( 8-quinolinol) zinc (Znq) and the like, and a metal complex in which the central metal of these metal complexes is substituted with In, Mg, Cu, Ca, Sn, Ga, or Pb can also be used as the electron transport material.

In addition, metal-free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group or a sulfonic acid group, etc. can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and inorganic semiconductors such as n-Si and n-SiC can also be used as the electron transport material, similar to the hole injection layer and the hole transport layer. have.

Further, it is also possible to use a polymer material in which these materials are introduced into the polymer chain, or in which these materials are used as the polymer main chain.

In the electron transport layer used in the present invention, the electron transport layer may be doped with a dope material as a guest material to form an electron transport layer having a high n property (electron rich). Examples of the dope material include n-type dopants such as metal complexes and metal compounds such as metal halide. As a specific example of the electron transport layer having such a structure, for example, Japanese Patent Laid-Open (Hei) 4-297076, 10-270172, Japanese Patent Laid-Open No. 2000-196140, 2001-102175, J . Appl. Phys., 95, 5773 (2004), etc. can be mentioned.

Specific examples of known preferable electron transporting materials used in the organic EL device of the present invention include compounds described in the following documents, but are not limited thereto.

US Patent No. 6528187, US Patent No. 7230107, US Patent Publication No. 2005/0025993, US Patent Publication No. 2004/0036077, US Patent Publication No. 2009/0115316, US Patent Publication No. 2009/ 0101870 specification, US patent publication 2009/0179554 specification, international publication 2003/060956, international publication 2008/132085, Appl. Phys. Lett. 75, 4(1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79, 156 (2001), US Patent No. 7964293, US Patent Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387, International Publication 2006/067931, International Publication No. 2007/086552, International Publication No. 2008/114690, International Publication No. 2009/069442, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011 /086935, International Publication No. 2010/150593, International Publication No. 2010/047707, European Patent No. 2311826, Japanese Patent Publication No. 2010-251675, Japanese Patent Publication No. 2009-209133, Japanese Patent Publication 2009-124114, Japanese Patent Publication No. 2008-277810, Japanese Patent Publication No. 2006-156445, Japanese Patent Publication No. 2005-340122, Japanese Patent Publication No. 2003-45662, Japanese Patent Publication 2003-31367, Japanese Patent Publication No. 2003-282270, International Publication No. 2012/115034, and the like.

As more preferable electron transport materials in the present invention, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, benzimidazole derivatives Can be mentioned.

The electron transporting material may be used alone, or may be used in combination of multiple types.

≪Hole blocking layer≫

The hole blocking layer is a layer having a function of an electron transport layer in a broad sense, and preferably includes a material having a function of transporting electrons and having a small ability to transport holes, and by blocking holes while transporting electrons, It is possible to improve the probability of recombination of holes.

Further, the above-described structure of the electron transport layer can be used as the hole blocking layer according to the present invention, if necessary.

It is preferable that the hole blocking layer provided in the organic EL device of the present invention is formed adjacent to the cathode side of the light emitting layer.

The layer thickness of the hole blocking layer used in the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.

As the material used for the hole blocking layer, the material used for the electron transport layer described above is preferably used, and the material used as the host compound described above is also preferably used for the hole blocking layer.

≪Electron injection layer≫

The electron injection layer (also referred to as ``cathode buffer layer'') used in the present invention is a layer formed between the cathode and the light emitting layer for lowering the driving voltage and improving the luminance of light emission, and is referred to as "organic EL devices and the forefront of industrialization (November 1998). Issued by NTS on the 30th)”, Chapter 2 of “Electrode Materials” (pages 123 to 166).

In the present invention, the electron injection layer may be formed as necessary, and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.

The electron injection layer is preferably a very thin film, and depending on the material, the layer thickness is preferably in the range of 0.1 to 5 nm. Further, it may be a non-uniform film in which the constituent material is intermittently present.

The electron injection layer is described in detail in Japanese Patent Laid-Open No. Hei 6-325871, 9-17574, 10-74586, and the like, and concretes of materials preferably used for the electron injection layer Examples include metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds typified by magnesium fluoride and calcium fluoride, metal oxides typified by aluminum oxide, lithium 8 -Metal complexes typified by hydroxyquinolate (Liq), etc. are mentioned. It is also possible to use the electron transport material described above.

In addition, the material used for the electron injection layer described above may be used alone or in combination of multiple types.

≪Hole transport layer≫

In the present invention, the hole transport layer may include a material having a function of transporting holes, and may have a function of transferring holes injected from the anode to the light emitting layer.

There is no particular limitation on the total thickness of the hole transport layer used in the present invention, but it is usually in the range of 5 nm to 5 μm, more preferably 2 to 500 nm, and still more preferably 5 nm to 200 nm.

As the material used for the hole transport layer (hereinafter, referred to as a hole transport material), it is sufficient to have any of hole injection or transport property and electron barrier property, and any one of conventionally known compounds can be selected and used.

For example, porphyrin derivative, phthalocyanine derivative, oxazole derivative, oxadiazole derivative, triazole derivative, imidazole derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, hydrazone derivative, stilbene derivative, polyaryl Alkane derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene or naphthalene, fluorene derivatives, fluorenone derivatives and polyvinylcarbazole, aromatic amines in the main or side chain Polymer materials or oligomers, polysilanes, conductive polymers or oligomers (for example, PEDOT:PSS, aniline-based copolymers, polyaniline, polythiophene, etc.) introduced into the material may be mentioned.

Examples of the triarylamine derivative include a benzidine type typified by αNPD, a starburst type typified by MTDATA, and a compound having fluorene or anthracene in the triarylamine linking core portion.

In addition, hexaazatriphenylene derivatives described in Japanese Patent Laid-Open No. 2003-519432 or Japanese Patent Laid-Open No. 2006-135145 can be similarly used as a hole transport material.

Further, a hole transport layer with a high p property doped with impurities may be used. As an example, JP-A-4-297076 A, JP-A-2000-196140, A-2001-102175, J. Appl. Phys., 95, 5773 (2004), etc. Can be mentioned.

In addition, the so-called p-type hole transport material or p-type described in Japanese Patent Laid-Open No. 11-251067, J. Huang et.al. (Applied Physics Letters 80 (2002), p.139). Inorganic compounds, such as -Si and p-type-SiC, can also be used. Further, an orthometalized organometallic complex having Ir or Pt as a central metal represented by Ir(ppy) ₃ is also preferably used.

As the hole transport material, the above can be used, but a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, azatriphenylene derivative, an organometallic complex, a polymeric material or oligomer in which an aromatic amine is introduced into the main chain or side chain And the like are preferably used.

As a specific example of the well-known and preferable hole transport material used in the organic EL device of the present invention, in addition to the above-mentioned documents, compounds described in the following documents may be mentioned, but the present invention is not limited thereto.

For example, Appl.Phys.Lett. 69, 2160 (1996), J. Lumin. 72-74, 985 (1997), Appl. Phys. Lett. 78, 673(2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Mater. Chem. 3, 319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15, 3148 (2003), US Patent Publication No. 2003/0162053, US Patent Publication No. 2002/0158242, US Patent Publication No. 2006/0240279, US Patent Publication No. 2008/0220265, US Patent No. 5061569 Specification, International Publication No. 2007/002683, International Publication No. 2009/018009, European Patent No. 650955, US Patent Publication No. 2008/0124572, US Patent Publication No. 2007/0278938, US Patent Publication No. 2008/0106190 Specification, US Patent Publication No. 2008/0018221 Specification, International Publication No. 2012/115034, Japanese Patent Publication No. 2003-519432, Japanese Patent Publication No. 2006-135145, US Patent Application No. 13/ 585981, etc.

The hole transport material may be used alone, or a plurality of types may be used in combination.

≪Electron blocking layer≫

The electron blocking layer is a layer having a function of a hole transport layer in a broad sense, and preferably includes a material having a function of transporting holes and having a small ability to transport electrons, and by blocking electrons while transporting holes, electrons and holes Can improve the probability of recombination.

In addition, the above-described configuration of the hole transport layer can be used as the electron blocking layer used in the present invention, if necessary.

It is preferable that the electron blocking layer provided in the organic EL device of the present invention is formed adjacent to the anode side of the light emitting layer.

The layer thickness of the electron blocking layer used in the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.

As the material used for the electron blocking layer, the material used for the hole transport layer described above is preferably used, and the material used as the host compound described above is also preferably used for the electron blocking layer.

≪Hole injection layer≫

The hole injection layer (also referred to as ``anode buffer layer'') used in the present invention means a layer formed between the anode and the light-emitting layer for lowering the driving voltage or improving the luminance of light emission, and "Organic EL devices and the forefront of industrialization thereof (1998). It is described in detail in Chapter 2 "Electrode Materials" (pages 123 to 166) of the second part of "November 30th issue of NTS Corporation)".

In the present invention, the hole injection layer may be formed as necessary, and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.

The hole injection layer is described in detail in Japanese Patent Laid-Open No. 9-45479, 9-260062, 8-288069, etc. As a material used for the hole injection layer, for example, For example, the material used for the above-described hole transport layer, etc. can be mentioned.

Among them, phthalocyanine derivatives represented by copper phthalocyanine, hexaazatriphenylene derivatives described in Japanese Patent Publication No. 2003-519432 or Japanese Patent Publication No. 2006-135145, metal oxides represented by vanadium oxide, and amorphous carbon , Conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes such as tris(2-phenylpyridine)iridium complexes, and triarylamine derivatives are preferable.

The material used for the above-described hole injection layer may be used singly, or a plurality of types may be used in combination.

≪Inclusions≫

The organic layer in the present invention described above may further contain other inclusions.

Examples of the content include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metals such as Pd, Ca, and Na, alkali metals, alkaline earth metals, and transition metals, complexes, and salts.

Although the content of the content can be arbitrarily determined, it is preferably 1000 ppm or less, more preferably 500 ppm or less, and still more preferably 50 ppm or less with respect to the total mass% of the layer to be contained.

However, it is not within this range depending on the purpose of improving the transport properties of electrons and holes, or the purpose of facilitating energy transfer of excitons.

≪Method of forming organic layer≫

A method of forming an organic layer (hole injection layer, hole transport layer, electron blocking layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) used in the present invention will be described.

The method of forming the organic layer used in the present invention is not particularly limited, and a conventionally known method of forming, for example, a vacuum evaporation method, a wet method (also referred to as a wet process), or the like can be used. Here, it is preferable that the organic layer is a layer formed by a wet process. That is, it is preferable to fabricate an organic EL device by a wet process. By fabricating the organic EL device by a wet process, effects such as a homogeneous film (coating film) can be easily obtained and a pinhole is difficult to be formed can be exhibited. In addition, the film (coating film) herein is in a state dried after application by a wet process.

As the wet method, there are spin coating method, cast method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, LB method (Langmuir-Blojet method), etc., but homogeneous From the viewpoint of easy to obtain a single thin film and high productivity, a method with high roll-to-roll suitability such as a die coating method, a roll coating method, an inkjet method, and a spray coating method is preferable.

As a liquid medium for dissolving or dispersing the organic EL material according to the present invention, for example, ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, and xylene , Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.

In addition, as a dispersion method, it can be dispersed by a dispersion method such as ultrasonic wave, high shear force dispersion, or media dispersion.

Further, different film forming methods may be applied for each layer. In the case of employing a vapor deposition method for film formation, the vapor deposition conditions vary depending on the type of compound used, but in general, boat heating temperature 50 to 450°C, vacuum degree 10 ^-6 to 10 ^-2 Pa, deposition rate 0.01 to 50 nm/sec. , It is preferable to appropriately select the substrate temperature in the range of -50 to 300°C, thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.

The organic layer used in the present invention is preferably formed from the hole injection layer to the cathode consistently in one vacuum, but may be taken out in the middle to perform a different film forming method. In that case, it is preferable to perform the operation in a dry inert gas atmosphere.

≪Anode≫

As the anode in the organic EL device, a metal having a large work function (4 eV or more, preferably 4.5 V or more), an alloy, an electrically conductive compound, and a mixture thereof are preferably used as an electrode material. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Further, a material capable of producing an amorphous transparent conductive film such as IDIXO (In ₂ O ₃ -ZnO) may be used.

For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern of a desired shape may be formed by a photolithography method, or when pattern precision is not very much required (about 100 μm or more), During deposition or sputtering of the electrode material, a pattern may be formed by passing through a mask having a desired shape.

Alternatively, in the case of using a material that can be applied such as an organic conductive compound, a wet film forming method such as a printing method or a coating method may be used. In the case of extracting light from the anode, the transmittance is preferably greater than 10%, and the sheet resistance as the anode is preferably several hundred ?/? or less.

The thickness of the anode varies depending on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

≪Cathode≫

As the cathode, a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as electrode materials. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium/copper mixture, magnesium/silver mixture, magnesium/aluminum mixture, magnesium/indium mixture, aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, Indium, lithium/aluminum mixtures, aluminum, and rare earth metals. Among these, from the viewpoint of durability against electron injection and oxidation, a mixture of an electron injectable metal and a second metal that is a more stable metal with a higher work function than this, for example, a magnesium/silver mixture, a magnesium/aluminum mixture, and magnesium /Indium mixture, aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, lithium/aluminum mixture, aluminum, etc. are suitable.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Further, the sheet resistance as the cathode is preferably several hundred Ω/□ or less, and the thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

In addition, since the emitted light is transmitted, it is preferable that the luminance of emission is improved when either the anode or the cathode of the organic EL element is transparent or semitransparent.

In addition, after preparing the metal to a thickness of 1 to 20 nm in the cathode, a transparent or semi-transparent cathode can be produced by fabricating the conductive transparent material exemplified in the description of the anode thereon. By applying this, both the anode and the cathode An element having this transmittance can be manufactured.

≪Support substrate≫

As a support substrate (hereinafter, also referred to as a substrate, a substrate, a substrate, a support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the kind of glass, plastic, and the like, and may be transparent or opaque. When light is extracted from the support substrate side, it is preferable that the support substrate is transparent. Glass, quartz, and a transparent resin film are mentioned as a transparent support substrate preferably used. A particularly preferable support substrate is a resin film capable of imparting flexibility to an organic EL element.

Examples of resin films include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, and cellulose acetate. Cellulose esters such as propionate (CAP), cellulose acetate phthalate, and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin , Polymethylpentene, polyether ketone, polyimide, polyether sulfone (PES), polyphenylene sulfide, polysulfone, polyetherimide, polyether ketoneimide, polyamide, fluororesin, nylon, polymethylmethacryl Cycloolefin resins, such as rate, acrylic, or polyarylates, Atone (made by a brand name JSR) or Arpel (made by a brand name Mitsui Chemical), etc. are mentioned.

On the surface of the resin film, a film of an inorganic substance or an organic substance or a hybrid film of both may be formed, and the water vapor transmission rate (25±0.5°C, relative humidity (90±2) measured by a method in accordance with JIS K 7129-1992) It is preferable that it is a barrier film having %RH) of 0.01 g/(m 2 ·24h) or less, and the oxygen permeability measured by a method in accordance with JIS K 7126-1987 is 10 ^-3 ml/(m 2 ·24h·atm) Hereinafter, it is preferable that it is a high-barrier film having a water vapor transmission rate of 10 ^-5 g/(m 2 ·24 h) or less.

As the material for forming the barrier film, any material that causes deterioration of the device, such as moisture or oxygen, but has a function of suppressing intrusion, may be used. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. In addition, in order to improve the fragility of the film, it is more preferable to provide a laminated structure of a layer containing these inorganic layers and organic materials. Although there is no restriction|limiting in particular about the lamination order of an inorganic layer and an organic layer, It is preferable that both are laminated|stacked alternately multiple times.

There is no particular limitation on the method of forming the barrier film, for example, a vacuum vapor deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric plasma polymerization method, plasma CVD method, Although a laser CVD method, a thermal CVD method, a coating method, or the like can be used, the atmospheric pressure plasma polymerization method described in Japanese Patent Laid-Open No. 2004-68143 is particularly preferred.

Examples of the opaque support substrate include a metal plate such as aluminum and stainless steel, a film or an opaque resin substrate, and a ceramic substrate.

The light emission quantum efficiency of the organic EL device of the present invention at room temperature is preferably 1% or more, and more preferably 5% or more.

Here, external extraction quantum efficiency (%) = number of photons emitted outside the organic EL element/number of electrons flowed through the organic EL element x 100.

Further, a color improving filter such as a color filter may be used in combination, or a color conversion filter for converting the luminescence color from the organic EL element into a polychromatic color using a phosphor may be used in combination.

≪Sealing≫

As the sealing means used for sealing the organic EL device of the present invention, for example, a method of bonding a sealing member, an electrode, and a supporting substrate with an adhesive can be mentioned. As the sealing member, it may be disposed so as to cover the display area of the organic EL element, and may be a concave plate shape or a flat plate shape. In addition, transparency and electrical insulation are not particularly limited.

Specifically, a glass plate, a polymer plate/film, a metal plate/film, etc. are mentioned. As a glass plate, especially soda-lime glass, barium-strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz, etc. are mentioned. Moreover, as a polymer plate, polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone, etc. are mentioned. Examples of the metal plate include those containing one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the organic EL device can be thinned. Further, the polymer film has an oxygen permeability of 1×10 ^-3 ml/(m 2 ·24h·atm) or less, measured by a method conforming to JIS K 7126-1987, and water vapor measured by a method conforming to JIS K 7129-1992. It is preferable that the transmittance (25±0.5° C., relative humidity (90±2)%) is 1×10 ⁻³ g/(m 2 ·24 h) or less.

Sandblasting, chemical etching, or the like is used to process the sealing member into a concave shape.

Specific examples of the adhesive include an acrylic acid-based oligomer, a photocurable and heat-curable adhesive having a reactive vinyl group of a methacrylic acid-based oligomer, and a moisture-curable adhesive such as 2-cyanoacrylic acid ester. Further, thermal and chemical curing types (two-liquid mixing) such as epoxy-based can be cited. Moreover, hot melt type polyamide, polyester, and polyolefin are mentioned. Further, a cationic curing type ultraviolet curable epoxy resin adhesive may be mentioned.

In addition, since the organic EL element may be deteriorated by heat treatment, it is preferable that it can be adhesively cured at a temperature from room temperature to 80°C. Further, a drying agent may be dispersed in the adhesive. For application of the adhesive to the sealing portion, a commercially available dispenser may be used, or printing may be performed such as screen printing.

Further, it is also suitable to form a sealing film by covering the electrode and the organic layer outside the electrode on the side opposite to the support substrate with the organic layer interposed therebetween, and forming a layer of an inorganic substance or an organic substance in contact with the support substrate. In this case, as a material for forming the film, any material that causes deterioration of the device, such as moisture or oxygen, but has a function of suppressing intrusion, may be used. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used.

In addition, in order to improve the fragility of the film, it is desirable to have a laminated structure of a layer containing these inorganic layers and organic materials. The method of forming these films is not particularly limited, and for example, a vacuum vapor deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric plasma polymerization method, plasma CVD method, A laser CVD method, a thermal CVD method, a coating method, or the like can be used.

It is preferable to inject an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicone oil into the gap between the sealing member and the display area of the organic EL element, as long as it is gaseous or liquid. It is also possible to use vacuum. In addition, a hygroscopic compound may be enclosed inside.

Examples of hygroscopic compounds include metal oxides (e.g., sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide, etc.), sulfates (e.g., sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate Etc.), metal halides (e.g., calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (e.g., barium perchlorate, magnesium perchlorate, etc.) And the like, and for sulfates, metal halides and perchloric acids, anhydrous salts are suitably used.

≪Shield, protective plate≫

A protective film or a protective plate may be formed on the outside of the sealing film or the sealing film on the side opposite to the support substrate with an organic layer therebetween in order to increase the mechanical strength of the device. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, so it is preferable to form such a protective film and a protective plate. As the material that can be used for this, a glass plate, a polymer plate/film, a metal plate/film, and the like similar to those used for the sealing can be used, but it is preferable to use a polymer film from the viewpoint of being lightweight and thinning.

≪Technology to improve light extraction≫

In general, an organic electroluminescent device emits light inside a layer having a higher refractive index than air (within a refractive index of about 1.6 to 2.1), and only about 15% to 20% of the light generated from the light emitting layer can be extracted. It is generally said that there is no. This means that light incident on the interface (interface between the transparent substrate and the air) at an angle θ greater than or equal to the critical angle causes total reflection and cannot be extracted to the outside of the device, and the light causes total reflection between the transparent electrode or the light emitting layer and the transparent substrate. This is because the transparent electrode or the light emitting layer is guided, and as a result, light escapes toward the side of the device.

As a method of improving the efficiency of light extraction, for example, a method of preventing total reflection at the interface between the transparent substrate and the air by forming irregularities on the surface of the transparent substrate (e.g., US Patent No. 4774435), A method of improving the efficiency by providing light condensing properties (for example, Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on the side of an element, etc. (for example, Japanese Patent Laid-Open (Pyeong) 1 -220394), a method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light-emitting body (for example, Japanese Patent Laid-Open No. 62-172691), between the substrate and the light-emitting body A method of introducing a flat layer having a lower refractive index than a substrate (for example, Japanese Patent Laid-Open No. 2001-202827), diffraction between the substrate and any layer of the transparent electrode layer or the light-emitting layer (including between the substrate and the outside world) A method of forming a lattice (Japanese Patent Application Laid-Open No. Hei 11-283751), etc. are mentioned.

In the present invention, these methods can be used in combination with the organic EL device of the present invention, but a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitting body, or between any layer of the substrate, the transparent electrode layer or the light emitting layer. A method of forming a diffraction grating on (including between the substrate and the outer space) can be suitably used.

In the present invention, by combining these means, it is possible to obtain an element having higher brightness or superior durability.

When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate to a thickness longer than the wavelength of light, the light emitted from the transparent electrode becomes higher in extraction efficiency to the outside as the medium has a lower refractive index.

Examples of the low refractive index layer include airgel, porous silica, magnesium fluoride, and fluorine-based polymers. Since the refractive index of the transparent substrate is generally in the range of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Moreover, it is more preferable that it is 1.35 or less.

In addition, it is preferable that the thickness of the low refractive index medium is at least twice the wavelength in the medium. This is because the effect of the low-refractive-index layer becomes blurred when the thickness of the low-refractive-index medium becomes about the wavelength of light and the electromagnetic wave exuded from Evanescent enters the substrate.

A method of introducing a diffraction grating into an interface or a medium that causes total reflection has a feature of having a high effect of improving light extraction efficiency. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by the so-called Bragg diffraction, which is called first order diffraction or second order diffraction. By introducing a diffraction grating between any layers or in a medium (in a transparent substrate or in a transparent electrode), a diffraction grating is used to diffract the light that cannot be emitted outside due to total reflection in the light, thereby extracting the light out.

It is preferable that the diffraction grating to be introduced has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution in only one direction, only light traveling in a specific direction is diffracted, so the efficiency of light extraction is very high. Does not rise.

However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, thereby increasing the efficiency of light extraction. The position where the diffraction grating is introduced may be between any layers or in a medium (in a transparent substrate or in a transparent electrode), but is preferably in the vicinity of the organic light-emitting layer, which is a place where light is generated. At this time, the period of the diffraction grating is preferably in the range of about 1/2 to 3 times the wavelength of light in the medium. It is preferable that the arrangement of the diffraction grating is repeated two-dimensionally, such as a square lattice image, a triangular lattice image, and a honeycomb lattice image.

≪Condensing sheet≫

The organic EL device of the present invention is processed to provide, for example, a structure on a microlens array on the light extraction side of the support substrate (substrate), or by combining it with a so-called light-converging sheet, By condensing light in the front direction, the luminance in a specific direction can be increased.

As an example of the microlens array, a square weight having a side of 30 mu m and a vertex angle of 90 degrees is arranged in two dimensions on the light extraction side of the substrate. One side is preferably within the range of 10 to 100 µm. If it is smaller than this, the effect of diffraction occurs and is colored. If it is too large, the thickness becomes thick, which is not preferable.

As the light-converging sheet, it is possible to use, for example, what has been put into practical use in an LED backlight of a liquid crystal display device. As such a sheet, for example, a brightness increasing film (BEF) manufactured by Sumitomo 3M can be used. As the shape of the prism sheet, for example, a Δ-shaped stripe having a 90 degree apex angle and a pitch of 50 µm may be formed on the substrate, a shape having a rounded apex angle, a shape in which the pitch is randomly changed, or other shapes.

Further, in order to control the light emission angle from the organic EL element, a light diffusion plate/film may be used in combination with a light collecting sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

≪Use≫

The organic EL element of the present invention can be used as a display device, a display, and various light sources. Examples of light-emitting light sources include lighting devices (home lighting, in-vehicle lighting), backlights for clocks and liquid crystals, billboard advertisements, signal devices, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, light sources for optical sensors. And the like, but the present invention is not limited thereto, but it can be particularly effectively used as a backlight for a liquid crystal display device and a light source for illumination.

In the organic EL device of the present invention, if necessary, patterning may be performed by a metal mask or inkjet printing method during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, the entire element layer may be patterned, and in fabrication of the element, a conventionally known method can be used.

≪Display device≫

Hereinafter, an example of a display device having an organic EL element of the present invention will be described based on the drawings.

Fig. 4 is a schematic perspective view showing an example of a configuration of a display device comprising an organic EL element of the present invention, and is a schematic diagram of a display such as a mobile phone, which displays image information by light emission of the organic EL element. As shown in Fig. 4, the display 1 includes a display unit A having a plurality of pixels, a control unit B for performing image scanning of the display unit A based on image information, and the like.

The control unit B is electrically connected to the display unit A. The control unit B transfers a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. As a result, each pixel sequentially emits light according to the image data signal for each scanning line by the scanning signal, and image information is displayed on the display portion A.

5 is a schematic diagram of the display portion A illustrated in FIG. 4.

The display portion A has a wiring portion including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3, and the like on a substrate.

The main members of the display portion A will be described below.

In FIG. 5, the case where light emitted from the pixel 3 is extracted in the direction of the white arrow (downward direction) is shown. The scanning line 5 and the plurality of data lines 6 of the wiring portion are each made of a conductive material. The scanning line 5 and the data line 6 are orthogonal to each other in a lattice shape, and are connected to the pixel 3 at a position perpendicular to each other (details not shown).

When a scanning signal is transmitted from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data.

Full-color display is possible by appropriately arranging pixels in the red region, pixels in the green region, and pixels in the blue region in parallel on the same substrate.

≪Lighting device≫

An embodiment of the lighting device of the present invention including the organic EL element of the present invention will be described.

Covering the non-luminous surface of the organic EL device of the present invention with a glass case, using a glass substrate having a thickness of 300 μm as a sealing substrate, and using an epoxy-based photocurable adhesive (Luxtrak LC0629B manufactured by Doa Kosei Co., Ltd.) as a sealing material around the It is applied, it is laminated on the cathode, and is in close contact with the transparent support substrate, and UV light is irradiated from the side of the glass substrate, cured, and sealed, so that an illumination device as shown in Figs. 6 and 7 can be formed.

6 shows a schematic diagram of a lighting device, and the organic EL element 101 of the present invention is covered with a glass cover 102 (in addition, the sealing operation by the glass cover is performed by bringing the organic EL element 101 into contact with the atmosphere. In a glove box under a nitrogen atmosphere (in an atmosphere of a high purity nitrogen gas of 99.999% or more in purity)).

7 is a cross-sectional view of the lighting device, and in FIG. 7, reference numeral 105 denotes a cathode, 106 denotes an organic layer (light emitting unit), and 107 denotes a glass substrate provided with a transparent electrode. Moreover, nitrogen gas 108 is filled in the glass cover 102, and the water catcher 109 is provided.

Example

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the indication of "part" or "%" is used in Examples, "part by mass" or "% by mass" is indicated unless otherwise specified.

<Example 1>

In addition, about the various compounds used in this example, the following compounds were used in addition to the compounds described above.

≪Preparation of luminescent thin film for evaluation≫

A quartz substrate having a thickness of 50 mm x 50 mm and a thickness of 0.7 mm was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, UV ozone cleaning was performed for 5 minutes, and then the transparent substrate was placed in a substrate holder of a commercially available vacuum vapor deposition apparatus. Fixed on. Each of the evaporation crucibles of the vacuum evaporation apparatus was charged so that the "host compound" and "dopant" shown in Table 1 would each be in an optimal amount for device fabrication. The vapor deposition crucible was made of a molybdenum resistance heating material.

After reducing the pressure in the vacuum evaporation apparatus to a degree of vacuum of 1×10 ^-4 Pa, the host compound and the dopant described in Table 1 were used, and the host compound and the dopant were co-deposited at a deposition rate of 0.1 nm/sec so that the volume ratio of Table 1 Then, the luminescent thin films 1, 2 and 3 for evaluation having a thickness of 30 nm were produced.

The luminescent thin films 1, 2 and 3 for evaluation were covered with a glass case in an atmosphere of high purity nitrogen gas of 99.999% or more, and a glass substrate having a thickness of 300 μm was used as a sealing substrate, and an epoxy-based photocurable type as a sealing material around the An adhesive (Luxtrac LC0629B manufactured by Toa Kosei Co., Ltd.) was applied, and this was brought into close contact with the quartz substrate, irradiated with UV light from the side of the glass substrate, cured, and sealed.

≪Measurement of emission spectrum of light-emitting thin film≫

The measurement of the emission spectrum was performed at room temperature (300K) using an F-7000 type spectroscopic fluorescence photometer manufactured by Hitachi. 8 shows emission spectra of the luminescent thin films 1, 2, and 3. The horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary unit). In both of the luminescent thin films 1 and 2, room temperature phosphorescence emission of the vicinity of 470 nm by the metal complex and fluorescence emission of the vicinity of 400 nm by the host compound are observed. Further, in the luminescent thin film 2 of the present invention, a new luminescence peak is observed in the vicinity of 360 nm, but not in the comparative thin film 1. This new luminescence peak around 360 nm is considered to be luminescence due to exciplex formation of a dopant and a host compound.

≪Emission life evaluation≫

According to the following method, the luminance residual ratio in the UV irradiation test using the HgXe light source was determined.

In the UV irradiation test using the HgXe light source, a mercury xenon lamp UV irradiation apparatus LC8 manufactured by Hamamatsu Photonics was used, and A9616-05 was attached to the UV cut filter and used. It was arrange|positioned so that the irradiation fiber light-exiting surface and the glass cover surface of a sample (a thin film for evaluation) were horizontal, and irradiated until the number of light emission photons was reduced by half at a distance of 1 cm. Measurement was performed under the conditions of room temperature (300K).

For each thin film for evaluation, the time required until the number of light-emitting photons was reduced by half (half-time), and a relative value (LT50 ratio) of the light-emitting thin film 1 at room temperature (300K) was 1.0.

In addition, the measurement of the luminance (the number of light emission photons) was measured with a spectral emission luminance meter CS-1000 (manufactured by Konica Minolta) from an angle inclined at 45 degrees from the axis of the irradiated fiber.

Table 2 shows the results of the luminescence lifetime. Compared to the comparative luminescent thin film 1, it can be seen that the light emitting lifetime of the luminescent thin film 2 of the present invention is significantly improved. In the luminescent thin film 2 of the present invention, it is considered that durability is improved by the formation of exciplexes of a dopant and a host compound.

≪Production of lighting equipment for evaluation≫

ITO (indium tin oxide) was formed as an anode on a glass substrate having a thickness of 50 mm x 50 mm and a thickness of 0.7 mm to a thickness of 150 nm, and after patterning, the transparent substrate on which the ITO transparent electrode was provided was prepared with isopropyl alcohol. After ultrasonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.

Each of the resistive heating boats for vapor deposition in the vacuum evaporation apparatus was filled with an optimum amount for each element fabrication of the constituent materials of each layer. The resistance heating boat was made of molybdenum or tungsten.

After reducing the pressure to a degree of vacuum of 1 × 10 ^-4 Pa, it was energized and heated to a resistance heating boat containing HI-1, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm/sec to form a hole injection layer having a thickness of 10 nm. .

Subsequently, HT-1 was deposited at a deposition rate of 0.1 nm/sec to form a hole transport layer having a thickness of 30 nm.

Subsequently, the resistance heating boat containing the "host compound" and "dopant" shown in Tables 3 to 5 is energized and heated, so that the host compound and the dopant are 85% by volume and 15% by volume, respectively, the vapor deposition rate of 0.085 nm/ Second, it was co-deposited on the hole transport layer at 0.015 nm/second to form a light emitting layer having a thickness of 30 nm. In addition, when two types of host compounds were used, the volume ratio was shown in parentheses in the column of the host compound.

Subsequently, HB-1 was deposited at a deposition rate of 0.1 nm/sec to form a first electron transport layer having a layer thickness of 5 nm. Further, ET-1 was deposited thereon at a deposition rate of 0.1 nm/sec to form a second electron transport layer having a layer thickness of 45 nm. Thereafter, lithium fluoride was vapor-deposited so as to have a layer thickness of 0.5 nm, and then aluminum 100 nm was vapor-deposited to form a cathode, and an organic EL device for evaluation was produced.

≪Measurement of emission spectrum≫

Also in the combination of the host compound and the dopant shown in Tables 3, 4, and 5, the luminescent thin films were each prepared by the same method as the production of the luminescent thin films 1 to 3, and the emission spectrum was measured. In the luminescent thin film according to the present invention, a new luminescence peak was observed in a region different from the thin film in which the host compound or the dopant was produced alone, and it was confirmed that exciplex was formed. In addition, among the luminescent thin films of the present invention, 1-15, 1-16, 1-17, 1-18, 2-11, and 2-12 are formed of two kinds of host compounds, and 1 Both exciplex light emission formed by the species host compound was observed. Meanwhile, it was confirmed that no new peaks existed in the luminescent thin film of Comparative Example.

In addition, in Tables 3, 4, and 5, in the evaluation of the luminescent thin film used in each lighting device, the case where the generation of exciplex was confirmed is indicated by ?, and the case where it is not confirmed is indicated by ?.

In addition, the presence or absence of the thermally active delayed fluorescence of the host compound was determined by transient PL measurement, and when it was confirmed, it was indicated as?

After fabrication of the organic EL device, the non-light emitting surface of the organic EL device was covered with a glass case in an atmosphere of high purity nitrogen gas of 99.999% or higher, and a glass substrate having a thickness of 300 µm was used as a sealing substrate, and as a sealing material around it. Applying an epoxy-based photocurable adhesive (Luxtrak LC0629B manufactured by Doa Kosei Co., Ltd.), superimposed on the cathode and in close contact with the transparent support substrate, irradiated with UV light from the side of the glass substrate, cured, and sealed, FIGS. A lighting device for evaluation including the configuration as shown in was produced.

≪Evaluation of continuous driving stability (half life)≫

For each evaluation lighting device, the luminance was measured using a spectroradiometer CS-2000, and the time (LT50) for the measured luminance to halve was determined as a half-life. The driving conditions were a current value of 15 mA/cm 2.

Table 3 is a comparison of BD-1, Table 4 is a comparison of BD-2, and Table 5 is a comparison of BD-3, and the evaluation lighting devices 1-1, 2-1 and 3-1 of each table are Relative values (half-life: relative value) with each half-life of 1.0 were calculated.

≪Evaluation of formula (I)≫

The energy level of the lowest air orbit of the phosphorescent metal complex is referred to as LUMO (D), the energy level of the highest target orbital of the host compound is referred to as HOMO (H), and the excitation singlet of the phosphorescent metal complex and the host compound The energy was compared, and when the lower energy level was S ₁ (min), the following formula (I) was satisfied using Gaussian98, which is a molecular orbital calculation software manufactured by Gaussian, the United States described above. In the following table, when the formula (I) was satisfied, it was described as "-", and when it became a positive (+) case without satisfying the formula (I), it was described as "+".

As shown in Table 3, for evaluation lighting devices 1-5 to 1-12, a combination in which a dopant satisfying the requirements of the present invention and a host compound form exciplex was used, and the stability of continuous driving was improved compared to the comparison. It could be confirmed that it is excellent. In addition, for the evaluation lighting devices 1-15 to 1-18, in addition to the dopant and the host compound, two types of host compounds were also used in combination to form exciplex, and as a result, it was confirmed that the continuous driving stability was further improved. . Table 4 and Table 5 can also confirm the same performance improvement.

From the above results, the effects of the present invention are summarized in Fig. 9. In Comparative 1 in Fig. 9, the probability that all host compounds can become excitons is high, and the stability is the lowest. In Comparative 2, since the host compound separated from the dopant is difficult to become an exciton, it is better than that of Comparative 1, but the host compound in the vicinity of the dopant is inferior to the present invention 1 because it can become an exciton. The present invention 2 is considered to have the highest stability because it can suppress the generation of excitons of host compounds in the vicinity of the dopant and remotely.

<Industrial availability>

The light-emitting thin film of the present invention has features of high luminous efficiency and a long luminous life, and can be used to provide an organic EL device with improved continuous driving stability. The organic EL element can be used as a display device, a display, and various light sources.

1: display
3: pixel
5: scan line
6: data line
A: display
B: control unit
101: organic EL element
102: glass cover
105: cathode
106: organic EL layer
107: transparent electrode mounting glass substrate
108: nitrogen gas
109: catcher

Claims (6)

A luminescent thin film comprising a phosphorescent metal complex having a structure represented by the following general formula (1) and having a property to emit light at room temperature, and a host compound forming an exciplex with the phosphorescent metal complex.

[In the general formula (1), M represents Ir or Pt. Each of A ₁ , A ₂ , B ₁ and B ₂ represents a carbon atom or a nitrogen atom. Ring Z ₁ represents a 6-membered aromatic hydrocarbon ring formed together with A ₁ and A ₂ , or a 5-membered or 6-membered aromatic heterocycle. Ring Z ₂ represents a 5- or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ . _One of the bonds of A ₁ and M and the bond of B ₁ and M is a coordination bond and the other represents a covalent bond. Ring Z ₁ and ring Z ₂ may each independently have a substituent, but at least one of the rings has a substituent having a structure represented by the general formula (2). By bonding the substituents of the ring Z ₁ and the ring Z ₂ , a condensed ring structure may be formed, or the ligands represented by the ring Z ₁ and the ring Z ₂ may be connected to each other. L represents a monoanionic bidentate ligand coordinated with M, and may have a substituent. m represents the integer of 0-2. n represents the integer of 1 to 3. When M is Ir, m+n is 3, and when M is Pt, m+n is 2. When m or n is 2 or more, the ligand or L represented by ring Z ₁ and ring Z ₂ may be the same or different, respectively, and the ligand and L represented by ring Z ₁ and ring Z ₂ may be connected.
In the general formula (2), * represents a linking point of the ring Z ₁ or ring Z ₂ in the general formula (1). L'represents a single bond or a linking group. Ar represents an electron acceptor substituent) delete The method according to claim 1, wherein at least two host compounds are contained, and at least one of them is capable of forming exciplexes with the phosphorescent metal complexes, and other types of host compounds form exciplexes. A luminescent thin film, characterized in that it has a property that can. The luminescent thin film according to claim 1 or 3, wherein the host compound that forms the phosphorescent metal complex and the exciplex is a compound exhibiting thermally active delayed fluorescence. The method of claim 1 or 3, wherein the energy level of the lowest air orbit of the phosphorescent metal complex is referred to as LUMO (D),
The energy level of the highest target orbital of the host compound forming the phosphorescent metal complex and the exciplex is called HOMO (H), and
When the singlet energy of excitation of the phosphorescent metal complex and the host compound is compared, and the lower energy level of any is S ₁ (min),
A luminescent thin film which satisfies the following formula (I).
Equation (I):

An organic electroluminescent device comprising at least a light emitting layer between an anode and a cathode, wherein the light emitting layer comprises the light emitting thin film according to claim 1 or 3.

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